The present invention relates to compressors including a gas compressing mechanism located in a chamber defined by a plurality of coupled housing elements. More specifically, the present invention pertains to a coupling structure for compressor housings and to a method for manufacturing and assembling compressors.
Swash plate type compressors are often used in vehicle air conditioners. The housing of a swash plate type compressor is generally constituted by a cylinder block, a front housing and a rear housing. The cylinder block has a plurality of cylinder bores. The front housing and the rear housing are secured to each end of the cylinder block with a sealing element such as an O-ring in between. A crank chamber is defined in the housing. The cylinder block has a shaft bore defined in the center portion. A radial bearing is located in the bore. The front housing also has a shaft bore defined in its center portion and a radial bearing located in the bore. A drive shaft extends through the crank chamber and is rotatably supported by the bearings located in the shaft bores of the cylinder block and the front housing. A swash plate is supported on the drive shaft in the crank chamber. The swash plate converts rotation of the drive shaft to reciprocation of pistons accommodated in the cylinder bores.
Accurate alignment of the axes of the shaft bores in the cylinder block and the front housing is required for smooth rotation of the drive shaft and accurate reciprocation of the pistons. Therefore, the front housing must be accurately positioned in relation to the cylinder block when joining the front housing with the cylinder block.
FIG. 5 shows one of the prior art methods for positioning a front housing in relation to a cylinder block. The method uses at least two positioning pins (only one is shown). As shown in FIG. 5, a pin hole 93 is formed in the upper portion and in the lower portion (only the pin hole in the upper portion is shown) of a cylinder block 92. The diameter of each pin hole 93 is substantially equal to that of the positioning pins 91. A front housing 94 has a pair of pin chambers 95, each corresponding to one of the pin holes 93 in the cylinder block 92. The diameter of the pin chambers 95 is larger than that of the pin holes 93.
When assembling the front housing 94 with the cylinder block 94, each pin 91 is arranged in a pair of the pin hole 93 and the pin chamber 95. A part of the inner wall 95a of each pin chamber 95 contacts the pin 91 and is aligned with a part of the inner wall 93a of the pin hole 93. The alignment determines the position of the front housing 94 in relation to the cylinder block 92.
However, the sizes of the positioning pins 91, the pin holes 93 and the pin chambers 95 have an error within a predetermined tolerance. When the front housing 94 is secured to the cylinder block 94 by using the positioning pins 91, the errors of the parts 91, 93, 95 are accumulated. The accumulation of the errors prevents an improvement in the positioning accuracy of the front housing 94 in relation to the cylinder block 92. In other words, the above prior art method, which uses the positioning pins 91, is not accurate enough to meet certain high standards.
O-rings are often used to seal between a cylinder block and a front housing. O-rings generally have standardized sizes and shapes. Therefore, when the design of a cylinder block and a front housing is changed, there may be no standard O-ring to conform to the changed cylinder block and front housing. Further, a groove must be formed in the end face of a cylinder block or of a front housing for accommodating an O-ring. These disadvantageous characteristics of O-rings have raised a need for a new type of a sealing member that conforms to changes in the size and shape of the cylinder block and the front housing.